Excellent review, Christophe, thank you! Must have been a fun experiment.
I’d like to offer some counterpoints to your #1 choice of the Nemo Nomad Air 30XL over the Exped Mega 12. I haven’t tried or even seen the Nomad. I do know the Expeds very well. So this comparison is based on the Nomad specs.
I have to question the premise that you don’t need insulation until you get into the 40s Fahrenheit. I’ve been cold on an uninsulated air mattress as soon as the temperature got into the 50s, with a 35F-degree down sleeping bag. The problem seems worse with a thicker mattress.
So that we’re comparing approximately the same size, I’ll use the mattresses you used, the Nemo Nomad 6 x 30 x 80, 47 oz, and the Exped Mega 12 LW 4.7 x 30.3 x 77.6. Here’s why the Exped is better:
1) The Exped weighs less . . .
2) . . . And yet it gives you, in my opinion, 50 degrees more warmth. Nemo doesn’t give an R value for the Nomad (or any of their mattresses, apparently). It’s probably less than 1. They give a temperature range, which has to subjective. I think that lessens Nemo’s credibility compared to Exped. The Nomad is basically a summer mattress. If you camp in cool or cold weather you would need a second mattress, which doubles your cost.
3) The Exped is available in four sizes. With the Nemo you’re stuck with the 30” width and the 80” length whether you need those or not. 30” is too wide for many cots. I have the Exped Mega 12 MW, which is 25.6 x 73.6 and a few ounces lighter.
Two more points to consider:
INFLATION: The review faults the Exped for awkward inflation. I complete agree that the large (brown) Pumpsack that comes with the Mega 12 is unwieldy. You need a lot of space and long arms to use it, and I’ve never been able to fill the sack more than 1/3 full. This problem is easily solved with the small yellow Pumpsack, which is a lot easier to fill. It takes about 4 to 6 sackfulls, less than two minutes, to fill the mattress. Works very well on a picnic table. Exped switched the sack for me for free. I’m guessing that the Nomad’s foot pump adds to the weight of the mattress. Would like to hear how effective it is.
THICKNESS: What’s the optimum thickness for comfort? 4”? 10”? 24”? At some point more thickness makes no further difference. In my experience, 2.5” is only moderately comfortable, especially for an older or heavier person. 3.5” is pretty good. 4.7” is perfect. I find no added comfort in 6” compared to 4.7”. If you use a cot, a thick mattress can feel too bouncy––you’ve got the bounciness of both the cot and the mattress.
THE VERDICT: Between the Nemo Nomad and the Exped Mega 12, the superiority of the Exped is in the INSULATION and the CHOICE OF SIZES. As the review hints, the vertical versus horizontal tubes don’t make a great difference in comfort. That’s in part because the tubes on the Exped Mega 12 have a very shallow depression. You can barely feel it. It feels like a supportive flat surface.
ONE MORE MATTRESS TO CONSIDER: If you use a cot, another mattress to consider is the Exped Synmat 3D-7 with boxed sides and a thickness of 2.5”. The MW size this brings the weight down to 33 oz. Works perfectly on a Helinox cot, better in fact than the thicker Mega 12 for the reason stated above. R value of 4.9 makes it a 3-season mattress.
Yah, I know I've beaten this topic to death. Gotta have something to do over the winter.